I've been digging around for about an hour and can't find the answer to my query. If I arrive CHI at Union Station (overnite train from NYC), where can I use a credit card to buy a CTA fare card so I can ride the bus a few times? I plan a 24-hour stop in CHI.

Or should I just bring a roll of quarters and drive everyone nuts dropping 9 of them in the onboard fare box each time?